Class DateFormat
- All Implemented Interfaces:
Serializable,Cloneable
- Direct Known Subclasses:
SimpleDateFormat
DateFormat is an abstract class for date/time formatting subclasses which
formats and parses dates or time in a language-independent manner.
The date/time formatting subclass, such as SimpleDateFormat, allows for
formatting (i.e., date → text), parsing (text → date), and
normalization. The date is represented as a Date object or
as the milliseconds since January 1, 1970, 00:00:00 GMT.
DateFormat provides static factory methods for obtaining default date/time
formatters based on the default or a given locale and a number of formatting
styles. The formatting styles include FULL, LONG, MEDIUM, and SHORT.
For any of the factory methods with the parameter style, an
IllegalArgumentException will be thrown if style is not equal to any
of the defined formatting styles. More detail and examples of using these styles are provided in the method
descriptions.
DateFormat helps you to format and parse dates for any locale.
Your code can be completely independent of the locale conventions for
months, days of the week, or even the calendar format: lunar vs. solar.
To format a date for the current Locale, use one of the static factory methods:
myString = DateFormat.getDateInstance().format(myDate);
If you are formatting multiple dates, it is more efficient to get the format and use it multiple times so that the system doesn't have to fetch the information about the local language and country conventions multiple times.
DateFormat df = DateFormat.getDateInstance(); for (Date myDate : dates) { output.println(df.format(myDate) + "; "); }
To format a date for a different Locale, specify it in the
call to getDateInstance().
DateFormat df = DateFormat.getDateInstance(DateFormat.LONG, Locale.FRANCE);
If the specified locale contains "ca" (calendar), "rg" (region override), and/or "tz" (timezone) Unicode extensions, the calendar, the country and/or the time zone for formatting are overridden. If both "ca" and "rg" are specified, the calendar from the "ca" extension supersedes the implicit one from the "rg" extension.
You can use a DateFormat to parse also.
myDate = df.parse(myString);
Use getDateInstance to get the normal date format for that country.
There are other static factory methods available.
Use getTimeInstance to get the time format for that country.
Use getDateTimeInstance to get a date and time format. You can pass in
different options to these factory methods to control the length of the
result; from SHORT to MEDIUM to LONG to FULL. The exact result depends
on the locale, but generally:
SHORTis the shortest and mainly numeric, such as12.13.52or3:30pmMEDIUMis longer, such asJan 12, 1952LONGis even longer, such asJanuary 12, 1952or3:30:32pmFULLis the longest, such asTuesday, April 12, 1952 AD or 3:30:42pm PST.
MEDIUM option,
and full text form is used with LONG and FULL options.
You can also set the time zone on the format if you wish.
If you want even more control over the format or parsing,
(or want to give your users more control),
you can try casting the DateFormat you get from the factory methods
to a SimpleDateFormat. This will work for the majority
of countries; just remember to put it in a try block in case you
encounter an unusual one.
You can also use forms of the parse and format methods with
ParsePosition and FieldPosition to
allow you to
- progressively parse through pieces of a string.
- align any particular field, or find out where it is for selection on the screen.
Synchronization
Date formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.
- API Note:
- Consider using
DateTimeFormatteras an immutable and thread-safe alternative. - Implementation Requirements:
- The
format(Date, StringBuffer, FieldPosition)andparse(String, ParsePosition)methods may throwNullPointerException, if any of their parameter isnull. The subclass may provide its own implementation and specification aboutNullPointerException. - The
setCalendar(Calendar),setNumberFormat(NumberFormat)andsetTimeZone(TimeZone)methods do not throwNullPointerExceptionwhen their parameter isnull, but any subsequent operations on the same instance may throwNullPointerException. - The
getCalendar(),getNumberFormat()andgetTimeZone()methods may returnnull, if the respective values of this instance is set tonullthrough the corresponding setter methods. For Example:getTimeZone()may returnnull, if theTimeZonevalue of this instance is set assetTimeZone(null).
- The
- Since:
- 1.1
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic classDefines constants that are used as attribute keys in theAttributedCharacterIteratorreturned fromDateFormat.formatToCharacterIteratorand as field identifiers inFieldPosition. -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intUseful constant for AM_PM field alignment.protected CalendarTheCalendarinstance used for calculating the date-time fields and the instant of time.static final intUseful constant for DATE field alignment.static final intUseful constant for DAY_OF_WEEK field alignment.static final intUseful constant for DAY_OF_WEEK_IN_MONTH field alignment.static final intUseful constant for DAY_OF_YEAR field alignment.static final intConstant for default style pattern.static final intUseful constant for ERA field alignment.static final intConstant for full style pattern.static final intUseful constant for zero-based HOUR_OF_DAY field alignment.static final intUseful constant for one-based HOUR_OF_DAY field alignment.static final intUseful constant for zero-based HOUR field alignment.static final intUseful constant for one-based HOUR field alignment.static final intConstant for long style pattern.static final intConstant for medium style pattern.static final intUseful constant for MILLISECOND field alignment.static final intUseful constant for MINUTE field alignment.static final intUseful constant for MONTH field alignment.protected NumberFormatThe number formatter thatDateFormatuses to format numbers in dates and times.static final intUseful constant for SECOND field alignment.static final intConstant for short style pattern.static final intUseful constant for TIMEZONE field alignment.static final intUseful constant for WEEK_OF_MONTH field alignment.static final intUseful constant for WEEK_OF_YEAR field alignment.static final intUseful constant for YEAR field alignment. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionclone()Overrides CloneablebooleanCompares the specified object with thisDateFormatfor equality.final StringBufferformat(Object obj, StringBuffer toAppendTo, FieldPosition fieldPosition) Formats the givenObjectinto a date-time string.final StringFormats aDateinto a date-time string.abstract StringBufferformat(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) Formats aDateinto a date-time string.static Locale[]Returns an array of all locales for which theget*Instancemethods of this class can return localized instances.Gets the calendar associated with this date/time formatter.static final DateFormatGets the date formatter with the default formatting style for the defaultFORMATlocale.static final DateFormatgetDateInstance(int style) Gets the date formatter with the given formatting style for the defaultFORMATlocale.static final DateFormatgetDateInstance(int style, Locale aLocale) Gets the date formatter with the given formatting style for the given locale.static final DateFormatGets the date/time formatter with the default formatting style for the defaultFORMATlocale.static final DateFormatgetDateTimeInstance(int dateStyle, int timeStyle) Gets the date/time formatter with the given date and time formatting styles for the defaultFORMATlocale.static final DateFormatgetDateTimeInstance(int dateStyle, int timeStyle, Locale aLocale) Gets the date/time formatter with the given formatting styles for the given locale.static final DateFormatGet a default date/time formatter that uses the SHORT style for both the date and the time.Gets the number formatter which this date/time formatter uses to format and parse a time.static final DateFormatGets the time formatter with the default formatting style for the defaultFORMATlocale.static final DateFormatgetTimeInstance(int style) Gets the time formatter with the given formatting style for the defaultFORMATlocale.static final DateFormatgetTimeInstance(int style, Locale aLocale) Gets the time formatter with the given formatting style for the given locale.Gets the time zone.inthashCode()Returns the hash code for thisDateFormat.booleanTell whether date/time parsing is to be lenient.Parses text from the beginning of the given string to produce a date.abstract Dateparse(String source, ParsePosition pos) Parse a date/time string according to the given parse position.parseObject(String source, ParsePosition pos) Parses text from a string to produce aDate.voidsetCalendar(Calendar newCalendar) Set the calendar to be used by this date format.voidsetLenient(boolean lenient) Specify whether or not date/time parsing is to be lenient.voidsetNumberFormat(NumberFormat newNumberFormat) Allows you to set the number formatter.voidsetTimeZone(TimeZone zone) Sets the time zone for the calendar of thisDateFormatobject.Methods declared in class java.text.Format
format, formatToCharacterIterator, parseObject
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Field Details
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calendar
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numberFormat
The number formatter thatDateFormatuses to format numbers in dates and times. Subclasses should initialize this to a number format appropriate for the locale associated with thisDateFormat. -
ERA_FIELD
public static final int ERA_FIELDUseful constant for ERA field alignment. Used in FieldPosition of date/time formatting.- See Also:
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YEAR_FIELD
public static final int YEAR_FIELDUseful constant for YEAR field alignment. Used in FieldPosition of date/time formatting.- See Also:
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MONTH_FIELD
public static final int MONTH_FIELDUseful constant for MONTH field alignment. Used in FieldPosition of date/time formatting.- See Also:
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DATE_FIELD
public static final int DATE_FIELDUseful constant for DATE field alignment. Used in FieldPosition of date/time formatting.- See Also:
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HOUR_OF_DAY1_FIELD
public static final int HOUR_OF_DAY1_FIELDUseful constant for one-based HOUR_OF_DAY field alignment. Used in FieldPosition of date/time formatting. HOUR_OF_DAY1_FIELD is used for the one-based 24-hour clock. For example, 23:59 + 01:00 results in 24:59.- See Also:
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HOUR_OF_DAY0_FIELD
public static final int HOUR_OF_DAY0_FIELDUseful constant for zero-based HOUR_OF_DAY field alignment. Used in FieldPosition of date/time formatting. HOUR_OF_DAY0_FIELD is used for the zero-based 24-hour clock. For example, 23:59 + 01:00 results in 00:59.- See Also:
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MINUTE_FIELD
public static final int MINUTE_FIELDUseful constant for MINUTE field alignment. Used in FieldPosition of date/time formatting.- See Also:
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SECOND_FIELD
public static final int SECOND_FIELDUseful constant for SECOND field alignment. Used in FieldPosition of date/time formatting.- See Also:
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MILLISECOND_FIELD
public static final int MILLISECOND_FIELDUseful constant for MILLISECOND field alignment. Used in FieldPosition of date/time formatting.- See Also:
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DAY_OF_WEEK_FIELD
public static final int DAY_OF_WEEK_FIELDUseful constant for DAY_OF_WEEK field alignment. Used in FieldPosition of date/time formatting.- See Also:
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DAY_OF_YEAR_FIELD
public static final int DAY_OF_YEAR_FIELDUseful constant for DAY_OF_YEAR field alignment. Used in FieldPosition of date/time formatting.- See Also:
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DAY_OF_WEEK_IN_MONTH_FIELD
public static final int DAY_OF_WEEK_IN_MONTH_FIELDUseful constant for DAY_OF_WEEK_IN_MONTH field alignment. Used in FieldPosition of date/time formatting.- See Also:
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WEEK_OF_YEAR_FIELD
public static final int WEEK_OF_YEAR_FIELDUseful constant for WEEK_OF_YEAR field alignment. Used in FieldPosition of date/time formatting.- See Also:
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WEEK_OF_MONTH_FIELD
public static final int WEEK_OF_MONTH_FIELDUseful constant for WEEK_OF_MONTH field alignment. Used in FieldPosition of date/time formatting.- See Also:
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AM_PM_FIELD
public static final int AM_PM_FIELDUseful constant for AM_PM field alignment. Used in FieldPosition of date/time formatting.- See Also:
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HOUR1_FIELD
public static final int HOUR1_FIELDUseful constant for one-based HOUR field alignment. Used in FieldPosition of date/time formatting. HOUR1_FIELD is used for the one-based 12-hour clock. For example, 11:30 PM + 1 hour results in 12:30 AM.- See Also:
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HOUR0_FIELD
public static final int HOUR0_FIELDUseful constant for zero-based HOUR field alignment. Used in FieldPosition of date/time formatting. HOUR0_FIELD is used for the zero-based 12-hour clock. For example, 11:30 PM + 1 hour results in 00:30 AM.- See Also:
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TIMEZONE_FIELD
public static final int TIMEZONE_FIELDUseful constant for TIMEZONE field alignment. Used in FieldPosition of date/time formatting.- See Also:
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FULL
public static final int FULLConstant for full style pattern.- See Also:
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LONG
public static final int LONGConstant for long style pattern.- See Also:
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MEDIUM
public static final int MEDIUMConstant for medium style pattern.- See Also:
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SHORT
public static final int SHORTConstant for short style pattern.- See Also:
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DEFAULT
public static final int DEFAULTConstant for default style pattern. Its value is MEDIUM.- See Also:
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Constructor Details
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DateFormat
protected DateFormat()Create a new date format.
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Method Details
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format
Formats the givenObjectinto a date-time string. The formatted string is appended to the givenStringBuffer.- Specified by:
formatin classFormat- Parameters:
obj- Must be aDateor aNumberrepresenting a millisecond offset from the Epoch.toAppendTo- The string buffer for the returning date-time string.fieldPosition- keeps track on the position of the field within the returned string. For example, given a date-time text"1996.07.10 AD at 15:08:56 PDT", if the givenfieldPositionisYEAR_FIELD, the begin index and end index offieldPositionwill be set to 0 and 4, respectively. Notice that if the same date-time field appears more than once in a pattern, thefieldPositionwill be set for the first occurrence of that date-time field. For instance, formatting aDateto the date-time string"1 PM PDT (Pacific Daylight Time)"using the pattern"h a z (zzzz)"and the alignment fieldTIMEZONE_FIELD, the begin index and end index offieldPositionwill be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character'z'.- Returns:
- the string buffer passed in as
toAppendTo, with formatted text appended. - Throws:
IllegalArgumentException- if theFormatcannot format the givenobj.- See Also:
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format
public abstract StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) Formats aDateinto a date-time string. The formatted string is appended to the givenStringBuffer.- Parameters:
date- a Date to be formatted into a date-time string.toAppendTo- the string buffer for the returning date-time string.fieldPosition- keeps track on the position of the field within the returned string. For example, given a date-time text"1996.07.10 AD at 15:08:56 PDT", if the givenfieldPositionisYEAR_FIELD, the begin index and end index offieldPositionwill be set to 0 and 4, respectively. Notice that if the same date-time field appears more than once in a pattern, thefieldPositionwill be set for the first occurrence of that date-time field. For instance, formatting aDateto the date-time string"1 PM PDT (Pacific Daylight Time)"using the pattern"h a z (zzzz)"and the alignment fieldTIMEZONE_FIELD, the begin index and end index offieldPositionwill be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character'z'.- Returns:
- the string buffer passed in as
toAppendTo, with formatted text appended.
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format
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parse
Parses text from the beginning of the given string to produce a date. The method may not use the entire text of the given string.See the
parse(String, ParsePosition)method for more information on date parsing.- Parameters:
source- AStringwhose beginning should be parsed.- Returns:
- A
Dateparsed from the string. - Throws:
ParseException- if the beginning of the specified string cannot be parsed.
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parse
Parse a date/time string according to the given parse position. For example, ifthishas the pattern"M/d/yy h:m a, z", then a time text"07/10/96 4:5 PM, PDT"will be parsed into aDatethat is equivalent toDate(837039900000L).By default, parsing is lenient: If the input is not in the form used by this object's format method but can still be parsed as a date, then the parse succeeds. Clients may insist on strict adherence to the format by calling
setLenient(false).This parsing operation uses the
calendarto produce aDate. As a result, thecalendar's date-time fields and theTimeZonevalue may have been overwritten, depending on subclass implementations. AnyTimeZonevalue that has previously been set by a call tosetTimeZonemay need to be restored for further operations.- Parameters:
source- The date/time string to be parsedpos- On input, the position at which to start parsing; on output, the position at which parsing terminated, or the start position if the parse failed.- Returns:
- A
Date, ornullif the input could not be parsed
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parseObject
Parses text from a string to produce aDate.The method attempts to parse text starting at the index given by
pos. If parsing succeeds, then the index ofposis updated to the index after the last character used (parsing does not necessarily use all characters up to the end of the string), and the parsed date is returned. The updatedposcan be used to indicate the starting point for the next call to this method. If an error occurs, then the index ofposis not changed, the error index ofposis set to the index of the character where the error occurred, and null is returned.See the
parse(String, ParsePosition)method for more information on date parsing.- Specified by:
parseObjectin classFormat- Parameters:
source- AString, part of which should be parsed.pos- AParsePositionobject with index and error index information as described above.- Returns:
- A
Dateparsed from the string. In case of error, returns null. - Throws:
NullPointerException- ifsourceorposis null.
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getTimeInstance
Gets the time formatter with the default formatting style for the defaultFORMATlocale.This is equivalent to calling
getTimeInstance(DEFAULT, Locale.getDefault(Locale.Category.FORMAT)).- Returns:
- a time formatter.
- See Also:
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getTimeInstance
Gets the time formatter with the given formatting style for the defaultFORMATlocale.This is equivalent to calling
getTimeInstance(style, Locale.getDefault(Locale.Category.FORMAT)).- Parameters:
style- the given formatting style. For example, SHORT for "h:mm a" in the US locale.- Returns:
- a time formatter.
- See Also:
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getTimeInstance
Gets the time formatter with the given formatting style for the given locale.- Parameters:
style- the given formatting style. For example, SHORT for "h:mm a" in the US locale.aLocale- the given locale.- Returns:
- a time formatter.
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getDateInstance
Gets the date formatter with the default formatting style for the defaultFORMATlocale.This is equivalent to calling
getDateInstance(DEFAULT, Locale.getDefault(Locale.Category.FORMAT)).- Returns:
- a date formatter.
- See Also:
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getDateInstance
Gets the date formatter with the given formatting style for the defaultFORMATlocale.This is equivalent to calling
getDateInstance(style, Locale.getDefault(Locale.Category.FORMAT)).- Parameters:
style- the given formatting style. For example, SHORT for "M/d/yy" in the US locale.- Returns:
- a date formatter.
- See Also:
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getDateInstance
Gets the date formatter with the given formatting style for the given locale.- Parameters:
style- the given formatting style. For example, SHORT for "M/d/yy" in the US locale.aLocale- the given locale.- Returns:
- a date formatter.
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getDateTimeInstance
Gets the date/time formatter with the default formatting style for the defaultFORMATlocale.This is equivalent to calling
getDateTimeInstance(DEFAULT, DEFAULT, Locale.getDefault(Locale.Category.FORMAT)).- Returns:
- a date/time formatter.
- See Also:
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getDateTimeInstance
Gets the date/time formatter with the given date and time formatting styles for the defaultFORMATlocale.This is equivalent to calling
getDateTimeInstance(dateStyle, timeStyle, Locale.getDefault(Locale.Category.FORMAT)).- Parameters:
dateStyle- the given date formatting style. For example, SHORT for "M/d/yy" in the US locale.timeStyle- the given time formatting style. For example, SHORT for "h:mm a" in the US locale.- Returns:
- a date/time formatter.
- See Also:
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getDateTimeInstance
Gets the date/time formatter with the given formatting styles for the given locale.- Parameters:
dateStyle- the given date formatting style.timeStyle- the given time formatting style.aLocale- the given locale.- Returns:
- a date/time formatter.
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getInstance
Get a default date/time formatter that uses the SHORT style for both the date and the time.- Returns:
- a date/time formatter
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getAvailableLocales
Returns an array of all locales for which theget*Instancemethods of this class can return localized instances. The returned array represents the union of locales supported by the Java runtime and by installedDateFormatProviderimplementations. At a minimum, the returned array must contain aLocaleinstance equal toLocale.ROOTand aLocaleinstance equal toLocale.US.- Returns:
- An array of locales for which localized
DateFormatinstances are available.
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setCalendar
Set the calendar to be used by this date format. Initially, the default calendar for the specified or default locale is used.Any
TimeZoneand leniency values that have previously been set are overwritten bynewCalendar's values.- Parameters:
newCalendar- the newCalendarto be used by the date format
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getCalendar
Gets the calendar associated with this date/time formatter.- Returns:
- the calendar associated with this date/time formatter.
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setNumberFormat
Allows you to set the number formatter.- Parameters:
newNumberFormat- the given new NumberFormat.
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getNumberFormat
Gets the number formatter which this date/time formatter uses to format and parse a time.- Returns:
- the number formatter which this date/time formatter uses.
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setTimeZone
Sets the time zone for the calendar of thisDateFormatobject. This method is equivalent to the following call.getCalendar().setTimeZone(zone);The
TimeZoneset by this method is overwritten by asetCalendarcall.The
TimeZoneset by this method may be overwritten as a result of a call to the parse method.- Parameters:
zone- the given new time zone.
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getTimeZone
Gets the time zone. This method is equivalent to the following call.getCalendar().getTimeZone();- Returns:
- the time zone associated with the calendar of DateFormat.
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setLenient
public void setLenient(boolean lenient) Specify whether or not date/time parsing is to be lenient. With lenient parsing, the parser may use heuristics to interpret inputs that do not precisely match this object's format. With strict parsing, inputs must match this object's format.This method is equivalent to the following call.
getCalendar().setLenient(lenient);This leniency value is overwritten by a call to
setCalendar().- Implementation Requirements:
- A
SPACE_SEPARATORin the input text will match any otherSPACE_SEPARATORs in the pattern with lenient parsing; otherwise, it will not match. - Parameters:
lenient- whentrue, parsing is lenient- See Also:
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isLenient
public boolean isLenient()Tell whether date/time parsing is to be lenient. This method is equivalent to the following call.getCalendar().isLenient();- Returns:
trueif thecalendaris lenient;falseotherwise.- See Also:
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hashCode
public int hashCode()Returns the hash code for thisDateFormat.- Overrides:
hashCodein classObject- Implementation Requirements:
- This method calculates the hash code value using the value returned by
getNumberFormat(). - Returns:
- the hash code for this
DateFormat - See Also:
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equals
Compares the specified object with thisDateFormatfor equality. Returns true if the object is also aDateFormatand the two formats would format any value the same.- Overrides:
equalsin classObject- Implementation Requirements:
- This method performs an equality check with a notion of class
identity based on
getClass(), rather thaninstanceof. Therefore, in the equals methods in subclasses, no instance of this class should compare as equal to an instance of a subclass. - Parameters:
obj- object to be compared for equality- Returns:
trueif the specified object is equal to thisDateFormat- See Also:
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clone
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